1. Field of the invention
The present invention concerns a novel family of thermotropic polymers the lateral chains of which have a chiral structure. The family of compounds according to the invention is formed from a monomer having the general chemical formula: EQU CH.sub.2 =C(R.sub.1)--COO--(CH.sub.2).sub.n --OR.sub.2
in which:
R.sub.1 is the methyl radical or an hydrogen or chlorine atom, PA1 n is an integer comprised between 2 and 11; and PA1 R.sub.2 is the group ##STR2## PA1 first step: synthesis of 2-methyl-1-bromobutane through the action of phosphorous tribromide upon 2-methyl-1-butanol; PA1 second step: synthesis of 4(3-methylbutyloxyphenol) through reaction of the 2-methyl-1-bromobutane obtained in the first step on hydroquinone; PA1 third step: synthesis of para-hydroxy-methyl-benzoic acid salt through esterification of 4-hydroxy-benzoic acid; PA1 fourth step: synthesis of para(hydroxyalkyloxy)-methyl-benzoic acid salt through reaction of w-bromoalcanol upon the parahydroxy-methyl-benzoic acid salt obtained in the third step: PA1 fifth step: synthesis of para(hydroxyalkyloxy)-benzoic acid through saponification of the ester obtained in the fourth step; PA1 sixth step: synthesis of 4(methacrylyloxy)alkoxy-benzoic acid, of 4(acrylyloxy)alkyloxy-benzoic acid or of 4(.alpha.-chloroacrylyloxy)alkoyloxy-benzoic acid through azeotropic esterification of the acid obtained in the fifth step with the methacrylic, acrylic or .alpha.-chloroacrylic acid respectively; PA1 seventh step: chloruration of the acid obtained in the sixth step; PA1 eighth step: synthesis of the monomer M.sub.1 through reaction of the acid chloride obtained in the seventh step and of the alkoxyphenol obtained in the second step; and PA1 ninth step: polymerization of the monomer M.sub.1 alone or in the presence of at least one other monomer.
The invention also concerns the process for manufacturing molecules of this family.
2. Description of the prior art
After the extraordinary development of research upon liquid crystals over the past fifteen years, due mainly to their potential practical utilization (their simplicity in ease of use low control tensions, low consumption) many research teams have directed their efforts towards research on mesomorphous polymers. Thermotropic mesomorphous polymers are macromolecules presenting, over a certain range of temperatures often relatively high, anisotropic phases called smectic or nematic phases. They comprise one class of polymers with mesogenic lateral groups and another class where the mesogenic group is comprised within the chain. The present invention concerns a family of polymers belonging to the first class specified above.
Although liquid crystals of low molecular weight crystallize at low temperature, the majority of thermotropic polymers with lateral chains are amorphous and are characterized by their vitreous transition temperature Tg. Both the macroscopic texture and the mesophasic range parameter can be frozen in the vitreous state.
Thereby, it is possible to obtain films having anisotropic optical properties that can be utilized in devices of the non-linear optical field.
Furthermore, the study of cholesteric phases allow to envisage the preparation of filters, reflectors and force measuring apparatus. In fact, it is possible to obtain, among others, through the intermediary of materials according to the invention, cholesteric thermotropic polymers. Furthermore, since the threshold tension values and the time intervals required for the orientation of the mesophases placed within an electrical field are of the same dimensions as those of the liquid crystals of low molecular weight, it is possible to consider that these polymers could be utilized in visualization devices intended for data memory storage.